Asks to join a listing whose leader reviews applications. Pick the listing from the autocomplete or type part of its title; the match is made among this server's open and full listings. If Group Finder is switched off for the server the reply is Not enabled.
A listing that is closed or unknown gives Listing not found or no longer active. You cannot apply to your own group: You can't apply to your own listing. If you are already seated, waitlisted or waiting on an application: You're already in this listing or have a pending application. If the leader removed you earlier: You were removed from this group by the leader and can't rejoin. On an open-join listing the reply sends you to /group join instead.
On success your reply is Application submitted for **{title}**. The leader will review it. The leader gets a DM headed New application naming you and the listing, with a pointer to /group approve and /group deny.
You can also press Apply on the listing card, which additionally lets you add a note for the leader. Applications are accepted on full listings too, but the leader cannot approve one until a seat is free.